1. Field of the Invention
The present disclosure relates to toner for electrophotography and developer containing the toner for electorophotography.
2. Description of the Related Art
An electrophotographic image forming apparatus such as a copier, a printer, a facsimile machine, and a multifunction peripheral of these, includes an image bearing member, a charging device that uniformly charges a surface of the image bearing member, an exposure device that forms an electrostatic latent image on the surface of the image bearing member by exposing the charged surface of the image bearing member based on image data, a developing device that develops the electrostatic latent image as a toner image by supplying toner to the surface of the image bearing member on which the electrostatic latent image has been formed, and a transfer device that transfer the toner constituting the toner image from the image bearing member to a recording medium. Using the aforementioned devices, the image forming apparatus transfers the toner image, which has been formed based on image data, to the recording medium, then forms an image on the recording medium by fixing the toner image onto the recording medium.
There is an increasing use of image forming apparatuses that not only perform monochrome printing, but are provided with a color printing function for forming color images. Specifically, image forming apparatuses such as single drum system color copiers and multifunction peripherals (MFPs) constituted by a single photosensitive drum are being used for example. However, when performing color printing on a single sheet with a single drum system image forming apparatus such as those, it is necessary to form an image on the photosensitive drum, which is the image bearing member, each time each color such as black, yellow, cyan, and magenta is to be developed on the paper. Accordingly, there is a problem that the printing speed when carrying out color printing drops to approximately one-quarter compared to the printing speed when carrying out monochrome printing. That is, there is a problem that color printing requires approximately four times the time compared to monochrome printing. Thus, shorter printing times, that is, faster printing speeds, are required for image forming apparatuses provided with a color printing function. Tandem system color image forming apparatuses and the like are put forth to satisfy these demands.
Specifically, for example, a tandem system color image forming apparatus is an image forming apparatus provided with an intermediate transfer belt for performing secondary transfer of a toner image to a transfer material such as paper after the toner image formed on the image bearing member has undergone primary transfer using an electrophotographic method, and forms a color image by superimposing multiple color toner images such as yellow (Y), magenta (M), cyan (C), and black (K) on the intermediate transfer belt. Image forming units corresponding to each color are provided in a row along the intermediate transfer belt in tandem system color image forming apparatuses for superimposing the toner images of multiple colors. Then, the toner images of the four colors YMCK formed by the photosensitive drum in each of the image forming units are transferred sequentially (primary transfer) so as to be superimposed over each other on intermediate transfer belt, thereby forming a color image. Then, the color image that is formed on the intermediate transfer belt is transferred (secondary transfer) onto the transfer material such as paper by a secondary transfer roller, which is arranged facing the intermediate transfer belt. In this way, a toner image corresponding to each color is formed on its respective image bearing member in each image forming unit, then these toner images are superimposed to form a color image, such that a tandem system color image forming apparatus achieves high speed printing. Here, a high-speed, low-temperature fixing process is used to fix the toner images onto the transfer material (a recording medium) also to achieve high speed printing.
On the other hand, to form high quality images, superior capabilities such as the following for example are required in the image forming apparatuses. First, superior toner color-producing qualities are required in the toner images (image) to be formed so as to achieve an image of high reproducibility based on the image data. Next, it is required to achieve high surface smoothness in the toner images (image) to be formed on the recording medium. By doing this, diffused reflection of light by the image surface is suppressed, and photo images and the like can be formed with high quality. Further still, superior fixing qualities are required. When there are superior fixing qualities over a long period, occurrences of an offset phenomenon or the like caused by the toner images adhering to the fixing rollers can be suppressed even though the images are formed repetitively, which may also contribute to improved smoothness in the image surface.
Thus, toner such as the following has been tested as toner to be used in the image forming apparatuses.
First, as a first example, toner was tested containing types of wax constituted by fatty acid ester, low melting point hydrocarbon, and high melting point hydrocarbon, having different endothermic peaks measured by DSC.
With this example, it is anticipated that no offset phenomenon will occur regardless of fixing conditions such as low temperature fixing or high temperature fixing due to the toner containing three types of waxes of different thermal characteristics. Further still, it is anticipated that occurrences of heat roller soiling will not occur even during long period usage and fixing qualities are superior using heavy papers also to which the fixing load tends not to be transmitted.
Furthermore, as a second example, an electrophotographic full color toner kit was tested constituted by a coloring toner, which is constituted by at least yellow toner, magenta toner, and cyan toner, and a colorless toner containing a release substance (wax) at 10 to 90 wt %.
With this example, it is anticipated that a toner kit can be provided that has color reproducibility, color mixing qualities, and transparency qualities due to a colorless toner being developed on the entire surface after the coloring toners of four colors have been developed, and further still that fixing offset can be prevented without coating a release agent on the fixing rollers.
Furthermore, methods such as the following have been tested as image forming methods using the image forming apparatuses.
As an example of the image forming methods, a multicolor image forming method has been tested in which, in a multicolor image forming method having a process in which multiple colored toner layers are fixed onto a transfer material (recording medium) as an image, and further having a process in which a transparent toner layer is fixed in an image area and a non-image area, and a surface mean roughness Ra and a maximum surface roughness Rmax of the fixed layers are set to predetermined surface roughnesses.
With this example, by having a process in which a transparent toner layer is fixed in an image area and a non-image area, and setting the surface mean roughness Ra and the maximum surface roughness Rmax of the fixed layers to predetermined surface roughnesses, it is anticipated that it will be possible to eliminate or suppress optical dispersion by the image surface, and to uniformly form a smooth high quality multicolor image, which has an appropriate gloss, excellent granularity, and high color tone, on the transfer material regardless of image type.